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Smart Fiber

New materials allow optical fibers with built-in electronic function.

Smart Fiber

Katrina Voss

May 30, 2012

Today’s high-speed fiber-optic communications marry electronics and optics—requiring semiconductor chips to convert light and optical fibers to carry the signal. But that technological merger can be cumbersome and inefficient. What if optical fibers could have the electronics built right in?

Badding Group, Penn State University

A cross section of the new optical fiber.

Potential applications would include improved telecommunications and laser technologies, more accurate remote-sensing devices, and similar upgrades in other optical-electronic hybrids.

That’s the promise of new crystalline materials developed by an international team of researchers led by John Badding, a professor of chemistry at Penn State.

“The optical fiber is usually a passive medium that simply transports light, while the chip is the piece that performs the electrical part of the equation,” Badding explains. A ‘smart fiber,’ by contrast, would have the electronic functions already included.

That kind of integration, however, has been difficult to achieve. For one thing, Badding says, optical fibers are round and cylindrical, while chips are flat, so simply shaping the connection between the two is a challenge. “An optical fiber is 10 times smaller than the width of a human hair,” he adds, and light-guiding pathways built onto chips are up to 100 times smaller than that. “So imagine just trying to line those two devices up.”

Instead, Badding and his colleagues used high-pressure chemistry techniques to deposit semiconducting materials directly, layer by layer, into tiny holes in optical fibers.

“The big breakthrough here is that we don’t need the whole chip as part of the finished product,” says Pier J. A. Sazio of the University of Southampton in the United Kingdom, another of the team’s leaders. “We have managed to build the junction—the active boundary where all the electronic action takes place—right into the fiber.”

Badding Group, Penn State University

Badding and his team built an optical fiber with a high-speed electronic junction—the active boundary where all the electronic action takes place—integrated adjacent to the light-guiding fiber core. Light pulses (white spheres) traveling down the fiber can be converted to electrical signals (square wave) inside the fiber by the junction. The potential applications of such optical fibers include improved telecommunications and other hybrid optical and electronic technologies and improved laser technology.

“Moreover, while conventional chip fabrication requires multimillion-dollar clean-room facilities, our process can be performed with simple equipment that costs much less,” Sazio notes.

One of the key goals of research in the field is to create a fast, all-fiber network, he says. “If the signal never leaves the fiber, then it is a faster, cheaper, and more efficient technology. If we can actually generate signals inside a fiber, a whole range of optoelectronic applications becomes possible.”